Dispatches from a Small Business

If Only the US Been Part of the Soviet Economy...

... then it would be much easier to reduce CO2 production, because we could just shut down stupid-inefficient boneheaded and outdated Soviet-era industry, like Poland has:

Polish Prime Minister reminded that the economy of Poland, who has cut
carbon emissions by about 30 percent since 1988, relies on coal for up
to 90 percent of its energy needs. This, he argued, entitles Poland to
encourage other countries, for whom climate protection is a hard nut to
crack.

Amount of Polish CO2 reduction that would not have happened anyway in the course of modernizing their economy and is instead due to focus on CO2: Zero.

More on how the vast majority of European progress towards Kyoto goals is due to the shutdown of Soviet industry, and how this is the primary reason the 1990 benchmark date was chosen, here.